Using simulation to define moisture availability and trafficability for a heavy clay soil in the Netherlands

Computer simulation was used in assessing moisture availability and trafficabillity of a heavy clay soil in grass. Calculations were made of the soil-moisture regime over a period of 30 years using measured meteorological and water-table data. Soil-physical input data consisted of moisture-retention and hydraulic-conductivity data, which were determined on large, undisturbed soil columns. The effect of vertical and horizontal soil cracks was assessed by independent quantitative measurements. Results of the calculations were expressed in terms of the probability of occurrence of: (1) precipitation deficits, (2) moisture deficits considering the calculated soil-moisture regime, and (3) adequate trafficability. Results referred to successive 10-day periods during the year. The magnitude of the moisture deficit was also expressed in terms of its yearly probability. Simulation models are essential tools for a flexible characterization of land qualities in terms of probability estimates which are useful for planning purposes.